Effects of sodium valproate on the serum protein binding of phenytoin, and on liver enzyme activity.
The effect of a single dose of sodium valproate on the serum protein binding of phenytoin was studied in 6 epileptic patients receiving phenytoin maintenance therapy. Phenytoin was significantly displaced by valproic acid, but the free concentration of phenytoin was unchanged because of redistribution to tissues. As a result of this effect, total serum phenytoin concentration was significantly lowered. Induction of metabolism probably does not play a part in this interaction because antipyrine half-lives and urinary D-glucaric acid excretion were not altered by chronic administration of sodium valproate to 8 patients receiving this drug alone.
D000983:Antipyrine / Q000097:blood; D001219:Aspartate Aminotransferases / Q000097:blood; D001798:Blood Proteins / Q000378:metabolism; D005937:Glucaric Acid / Q000652:urine; D006207:Half-Life; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D010672:Phenytoin / Q000097:blood*; D011485:Protein Binding / Q000187:drug effects; D013997:Time Factors; D014635:Valproic Acid / Q000494:pharmacology*
D001798:Blood Proteins; D014635:Valproic Acid; D010672:Phenytoin; D001219:Aspartate Aminotransferases; D005937:Glucaric Acid; D000983:Antipyrine